Optimizing CdZnTe Detectors to Discover High Energy Transient Phenomena

Abstract

Understanding the zoo of transient astronomical phenomena is critical to unveiling the underlying physics of compact objects, but such studies require improved scientific instrumentation and data analysis techniques to increase the number of observed transients. The High-Resolution Energetic X-ray Imager (HREXI) is an instrument design for a future wide-field coded aperture imaging x-ray telescope, the HREXI SmallSAT Extremes Explorer (HSEE) and will support the advancement of time-domain and multi-messenger astrophysics. In this thesis, I seek to increase the number of high-energy transients that HREXI will discover by expanding the instrument’s energy band coverage and improving the resolution of its Cadmium Zinc Telluride (CdZnTe) detectors through tuning of the Application Specific Integrated Circuit (ASIC) readout to allow stable operation in a low-noise mode called “Charge Pump Mode” (CPM). To achieve this, I developed equipment necessary for probing unattached ASICs for isolated testing, optimized the CPM parameter tuning process, and characterized a fully integrated detector unit in our newly developed thermal vacuum chamber. I also analyzed photometric light curves of Black Hole Low Mass X-ray Binaries (BH-LMXBs) from the Swift/Burst Alert Telescope (BAT) Transient Monitor, and explored novel methods for handling spacecraft dither corrections to counteract instrumental systematics. These methods can be applied to future HSEE operations to search for previously undetected short duration flaring of BH-LMXBs, thereby better measuring the BH-LMXB population.